Apparatus and methods relating to enhanced spectral measurement systems

ABSTRACT

The apparatus and methods herein provide light sources and spectral measurement systems that can improve the quality of images and the ability of users to distinguish desired features when making spectroscopy measurements by providing methods and apparatus that can improve the dynamic range of data from spectral measurement systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 10/952,374, filed 27 Sep. 2004, now U.S. Pat. No. 7,692,784,issued 6 Apr. 2010, which application claims the benefit of U.S.Provisional Patent Application No. 60/506,408, filed 26 Sep. 2003, nowexpired; all of the foregoing applications are incorporated herein byreference in their entireties.

BACKGROUND

Optical spectroscopy is a known method of measuring the opticalproperties of a material such as gas, liquid, solid, chemical compound,biological material such as biological fluids or tissue, paint orcoating or other material.

A common form of spectroscopy measures the spectral properties of thedesired material by illuminating the material with light and thenmeasuring the light remitted or emitted by a material. The relativeresponse of the material to light of different energy levels is usefulcharacteristic of a material, sometimes called the optical signaturethat can be used to identify the nature of a material or determine howmuch of a material is present.

When there is a mixture of materials the optical signature of themixture is typically some combination of the optical signatures of thecomponents of the mixture. Analysis of the relative amounts ofwavelengths characteristic of a particular material either by visualinspection, or more commonly by computer based algorithms, can be usedto determine how much of a material is present in the mixture.

The optical signatures or spectra of a material are typicallyrepresented as an intensity of emission or absorbance at a particularwavelength or wavelength range and are often presented as a twodimensional graph with wavelength on one axis and intensity orabsorbance as a function of wavelength on the other axis. These graphscan be simple or complex in shape and the range between intensities orabsorbance can be very great for different wavelengths.

The measurement tools used to measure the intensity of absorbance oremission of light from a compound are usually referred to asspectrographs or spectrometers and are well known. One limitation ofthese devices is the difficulty of making accurate measurements overwide ranges of intensity values.

Considering the case of reflectance spectroscopy, for some samples thelight emitted from a sample may be very bright at some wavelengths ofinterest and very faint at others. Often the detector measurement rangeis exceeded.

Detectors also often have their own wavelength response due to thespectral properties of the detection system, which can further limit thecapability to make an accurate measurement.

Most spectrometers are designed to work with a light source suitable forilluminating the material to be measured to provide wavelengths usefulfor measurement of the desired optical properties of the material. Themeasurement device is typically calibrated against the opticalproperties of the light source. This can also become a limiting factorin the ability of the system to make measurements since some lightsources do not provide enough of the wavelengths useful for themeasurement.

Often a spectrograph or spectrometer system has to be set up for aparticular application or a material to be measured and is difficult toreconfigure quickly for the measurement of a wide range of compounds.

Thus there has gone unmet a need for spectral measurement systems andspectroscopy light sources that provide improved dynamic range andimproved accuracy, and can be configured quickly to measure accurately awide range of samples.

SUMMARY

The apparatus and methods, etc., herein provide spectral measurementsystems (i.e., systems that measure the wavelength dependent intensitydistribution of light emanating from a sample) such as spectroscopysystems, the spectral measurement systems comprising acomputer-controlled illumination system (CCIS) and an operably linkedspectral measurement sensor (SMS), which can be an operably linkedcomputer-controlled spectral measurement sensor (CCSMS). The CCIS worksinteractively with the SMS to produce enhanced measurements such asmeasurements with expanded dynamic range, improved measurement signal tonoise ratio, or improved accuracy.

The computer-controlled illumination system comprises a tunable lightsource capable of providing illumination light having a variableselected spectral output and a variable wavelength dependent intensitydistribution. In certain embodiments, the CCIS comprises a bright sourceof broad-band visible illumination commonly called white light, aspectrum former such as a prism or diffraction grating, and a spatiallight modulator (SLM) such as a pixelated SLM, or other suitable tunabledevices such as transmissive SLMs, reflective SLMs, tunable devices suchas transmissive SLMs, reflective SLMs (such as digital micromirrordevices (DMDs) or liquid crystal on silicon devices (LCOSs)), oracousto-optic tunable filters (AOTFs). For example, the light from thelight source is directed as a beam to the wavelength dispersive element,which disperses the beam into a spectrum imaged onto the SLM. The pixelelements (or other light control elements) of the SLM can be rapidlyswitched to allow selected wavelengths of light and selected amounts ofthe selected wavelengths of light to form the illumination light and topropagate. The light that propagates is then optically mixed togetherand directed to the illumination path of a spectroscopy device orsystem.

While the use of white light is one preferred embodiment of the CCIS, itis also possible to use other wavelengths for example ultraviolet orinfrared, or to use narrower bands of illumination or light sources withstrong characteristic emissions which may be useful for measurements,for example a mercury arc lamp which has strong emissions at 365 nm, 405nm, 436 nm, 546 nm and other wavelengths, which may be useful forexciting fluorescence.

The SLM is operably connected to a controller, which controller containscomputer-implemented programming that controls the on/off pattern of thepixels in the SLM. The controller can be located in any desired locationto the rest of the system. For example, the controller can be eitherwithin a housing of the source of illumination or it can be locatedremotely, connected by a wire, fiber optic cable, cellular link or radiolink to the rest of the system. If desired, the controller, which istypically a single computer but can be a plurality of linked computers,a plurality of unlinked computers, computer chips separate from a fullcomputer or other suitable controller devices, can also contain one ormore computer-implemented programs that provide specific lightingcharacteristics, i.e., specific desired, selected spectral outputs andwavelength dependent intensities, corresponding to known wavelengthbands that are suitable for measuring the spectral property of a samplematerial.

In one aspect, the present apparatus and methods provides a CCIS thatprovides a variable selected spectral output and a variable selectedwavelength dependent intensity distribution wherein the CCIS comprises alight path that comprises: a) a spectrum former able to provide aspectrum from a light beam traveling along the light path, and b) apixelated SLM located downstream from and optically connected to thespectrum former, the pixelated SLM reflecting substantially all lightimpinging on the SLM and in some embodiments switchable to reflect lightfrom the light beam between at least first and second reflected lightpaths in which at least one or more of the light paths do not reflectback to the spectrum former. The SLM can, for example, be a digitalmicromirror device or LCOS. The SLM is operably connected to at leastone controller containing computer-implemented programming that controlsan on/off pattern of pixels in the pixelated SLM to reflect a desiredsegment of light in the spectrum to the first reflected light path andreflect substantially all other light in the spectrum impinging on theSLM to another light path, the desired segment of light consistingessentially of a desired selected spectral output and a desiredwavelength dependent intensity distribution.

The spectrum former can comprise at least one of a prism and adiffraction grating, which can be a reflective diffraction grating,transmission diffraction grating, variable wavelength optical filter, ora mosaic optical filter. The system may or may not comprise, between thespectrum former and the SLM, an enhancing optical element that providesa substantially enhanced image of the spectrum from the spectrum formerto the SLM. The SLM can be a first SLM, and the desired segment of lightcan be directed to a second SLM operably connected to the samecontroller or another controller containing computer-implementedprogramming that controls an on/off pattern of pixels in the second SLMto reflect the desired segment or other segment of light in onedirection and reflect other light in the spectrum in at least one otherdirection. The system can further comprise an optical projection devicelocated downstream from the first SLM to project light out of thelighting system as a directed light beam.

The CCIS can further comprise an illumination light detector opticallyconnected to and downstream from the SLM, the illumination lightdetector also operably connected to a controller containingcomputer-implemented programming able to determine from the illuminationlight detector whether the desired segment contains a desired selectedspectral output and a desired wavelength dependent intensitydistribution, and adjust the on/off pattern of pixels in the pixelatedSLM to improve the correspondence between the desired segment and thedesired selected spectral output and the desired wavelength dependentintensity distribution. The illumination light detector can be locatedin the light path of at least one other direction, and can comprise atleast one of a CCD, a CID, a CMOS, and a photodiode array.

In another aspect, the present apparatus and methods provides a standalone light source comprising a CCIS as discussed herein having avariable selected spectral output and wavelength dependent intensitydistribution and sized to project light onto a sample material. The CCIScan comprise the various elements discussed herein and a projectionsystem optically connected to and downstream from the SLM, wherein theprojection system projects the desired segment as a directed light beamto illuminate the material.

Similar projection systems can also be incorporated within light sourcescontained within a single housing containing the other components of thespectral measurement systems herein. For example, the high output lightsource, the spectrum former, the enhancing optical element that providesan enhanced image, the SLM, the projection system, etc., can all belocated in a single housing, or fewer or more elements can be located ina single housing.

The source of illumination can also comprise a heat management systemoperably connected to the tunable light source to remove undesiredenergy emitted from the light source toward at least one of the SLM andthe spectrum former. The CCIS can for example comprise a heat removalelement operably connected to the light source to remove undesiredenergy emitted from the light source toward at least one of the SLM, theenhancing optical element, and the spectrum former. The heat removalelement can for example be located between the spectrum former and afirst SLM, between the lamp and the spectrum former, or elsewhere asdesired. The heat removal element can comprise a dichroic mirror. Thedichroic mirror can transmit desired wavelengths and reflect undesiredwavelengths, or vice-versa. The undesired energy can be directed to anenergy absorbing surface and thermally conducted to a radiator. The heatremoval element can be an optical cell containing a liquid that absorbsundesired wavelengths and transmits desired wavelengths. The liquid canbe substantially water and can flow through the optical cell via aninlet port and outlet port in a recirculating path between the opticalcell and a reservoir. The recirculating path and the reservoir cancomprise a cooling device, which can be a refrigeration unit, athermo-electric cooler, or a heat exchanger.

The CCIS further can comprise a spectral recombiner optically connectedto and located downstream from the spatial light modulator, whichrecombiner can for example comprise a prism, a Lambertian opticaldiffusing element, a directional light diffuser such as a holographicoptical diffusing element, a lenslet array, or a rectangular light pipe.In one embodiment, the spectral recombiner can comprise an operablecombination of a light pipe and at least one of a lenslet array and aholographic optical diffusing element.

The CCIS or spectral measurement system can if desired comprise anadapter or other apparatus for mechanically and/or optically connectingthe illumination light guide of a spectrometer or other spectralmeasurement system to the output of the light source. The illuminationlight guide of the spectrometer can be at least one of an optical fiber,optical fiber bundle, liquid light guide, hollow reflective light guide,or free-space optical connector. The light guide may be integral withthe spectrometer or it may be modular and separable from thespectrometer.

In some aspects of the apparatus and methods, the illumination light isdirected to illuminate a material such that light emanating from thematerial, which light may or may not be the emanation light used forspectral measurements, is also used for imaging. Such images can beeffected using a sensor such as a photodetector, photodiode array, CCDdetector, CMOS detector, avalanche photodiode, or other type of imagingdevice.

In some aspects of the apparatus and methods, the illumination light isdirected to illuminate a material such that light is transmitted throughthe material or through a container, sampling window, cuvette or otheroptical path containing the material such that transmitted light that isnot absorbed by the material can be measured by an optical measurementsensor.

In some aspects of the apparatus and methods, the illumination light isdirected to illuminate a material such that it excites fluorescence (orother emitted light) in the material and fluorescent light is emittedfrom the material or through a container, sampling window, cuvette orother optical path containing the material and can be measured by anoptical measurement sensor.

In some embodiments of the apparatus and methods the SMS of thespectrometer can be an unfiltered sensor. An unfiltered image sensorrelies on the natural optical response of the sensor material to lightimpinging on the sensor to generate spectroscopy data signal. The SMScan for example be a photodetector, photodiode array, CCD detector, CMOSdetector, avalanche photodiode, or other type of spectral measurementdevice such as single sensor element, linear array of sensor elements,or two dimensional array of sensing elements such as a staring arraydetector.

In certain embodiments of the apparatus and methods the SMS can have anoptical filter placed in front of it to limit the wavelengths of lightthat reach the sensor. Exemplary sensors include linearly variablefilters, matrix filters, long-pass filters, short-pass filters,band-pass filters, or band-blocking filters. The matrix optical filtercan be at least two of a long-pass filter, a short-pass filter, aband-pass filter, or a band-blocking filter. A long-pass filter can beuseful to block undesired wavelengths such as ultraviolet light orfluorescence excitation light from impinging on the sensor. A short-passfilter can be useful to block undesired wavelengths such as infraredlight from impinging on the sensor. A band-pass filter can be useful toallow only selected wavelengths such as visible light to impinge on thedetector. A band-blocking filter can be useful to block fluorescenceexcitation light from impinging on the sensor. A linearly variablefilter can be useful to block higher orders of diffraction impinging ona sensor when a diffraction grating is used as a wavelength dispersiveelement in the SMS.

The SMS may also be a sensor that has a wavelength dispersive element,interposed between it and the light emanated from the material beingmeasured, that causes the light to be dispersed across an array ofsensing elements, each sensing element being calibrated so it isassociated with a particular wavelength of light.

In some embodiments of the apparatus and methods, the SMS can besynchronized to the CCIS to provide sequences of measurements of thewavelength dependent energy distribution of material illuminated bydesired wavelengths of light and captured as digital data. This digitaldata can then be combined or processed as desired to provide usefulinformation as desired.

In some embodiments of the apparatus and methods, the SMS can besynchronized to the CCIS to provide sequences of measurements of amaterial illuminated by desired wavelengths of light and captured asdigital spectral measurement data. The digital spectral measurement datacan then be combined or processed as desired to provide usefulinformation, to determine the illumination patters of the CCIS, orotherwise as desired.

The apparatus and methods can also comprise a SMS synchronized to theCCIS where the SMS is operated as a null detector, and the spectraloutput of the CCIS is adjusted until the intensity value at theillumination light detector and/or the SMS is null or constant at allwavelengths, and the information about the attenuated illumination isused to derive the spectral profile of the material being illuminated.

In a preferred embodiment of the apparatus and methods, the spectralmeasurement system or SMS provides a data capture device or sub-systemable to accept a digital or analog spectrometer signal provided by anexisting commercial spectrometer or spectral measurement system or acustom designed spectroscopy system constructed in a similar manner toan existing commercial spectroscopy system. The data capture device maybe integral to the CCIS or it may be a modular component of aspectroscopy system. It may be operably connected to a controllercontaining computer implemented programming that controls at least oneof the various components of the spectral measurement system.

In other embodiments, the controller contains computer implementedprogramming that can analyze the spectrum/spectra data of the materialcaptured from the SMS and if desired adjust the intensity of theillumination of the material to provide a measured spectrum that isenhanced for the operating range of the SMS.

In further embodiments, the controller contains computer implementedprogramming that can analyze the spectrum/spectra data of the materialcaptured from the SMS and if desired adjust the intensity of theillumination of the material to provide a measured spectrum that isenhanced for the operating range of the sensor, and then apply theinformation used to adjust the illumination light to scale the capturedspectroscopy data in a way suitable to present the measured spectraldata while restoring the appropriate relationships between theintensities of the measurement for each desired wavelength (typically,all wavelengths) while expanding the dynamic range of the measurement.

The CCIS and SMS may be operably connected to a controller, whichcontroller contains computer-implemented programming that controls thetiming of data acquisition in the SMS and the wavelength distributionand duration of illumination in the CCIS. The controller or thespectroscopy data measurement sub-system can be located in any desiredlocation to the rest of the system. For example, the controller can beeither within a housing of the source of illumination or it can belocated remotely, connected by a wire, fiber optic cable, cellular linkor radio link to the rest of the system. If desired, the controller,which is typically a single computer but can be a plurality of linkedcomputers, a plurality of unlinked computers, computer chips separatefrom a full computer or other suitable controller devices, can alsocontain one or more computer-implemented programs that provide controlof spectroscopy data acquisition and/or control of specific lightingcharacteristics, i.e., specific desired, selected spectral outputs andwavelength dependent intensities, corresponding to known wavelengthbands that are suitable for spectroscopy.

The spectral measurement system can further comprise computer controlledspectral data acquisition and processing systems that can analyze theinformation from the spectral measurement data or sequence of spectralmeasurement data and present it in a way that is meaningful to a humanoperator.

In a further aspect, the present apparatus and methods provides methodsof taking spectral measurements of a material comprising: a) directing alight beam along a light path and via a spectrum former to provide aspectrum from the light beam; b) propagating the spectrum by a tunablelight filter such as an SLM that provides a desired segment of light inthe spectrum to provide an illumination light consisting essentially ofa selected spectral output and a selected wavelength dependent intensitydistribution, transmitting the illumination light to a sample, thensensing a spectrum representing the sample, for example a spectrumreflecting from, transmitted through, or emitted from the sample, or aspectrum derived from a compensation scheme wherein the spectrum of thesample is created to provide a null response and the illumination lightadjustments to create the null response are determined.

The methods further can comprise emitting the light beam from a lightsource located in a same housing as and upstream from the spectrumformer. The methods further can comprise switching the modified lightbeam between a first reflected light path and a second reflected lightpath. The methods further can comprise passing the light beam by anenhancing optical element between the spectrum former and the SLM orother SLM to provide a substantially enhanced image of the spectrum fromthe spectrum former to the SLM.

The methods can further comprise sending the illumination light to anillumination light detector optically connected to and downstream fromthe SLM. The illumination light detector may be located in a secondreflected light path or otherwise as desired. The illumination lightdetector can be operably connected to a controller, the controllercontaining computer-implemented programming able to determine from theillumination light detector whether the illumination light contains thedesired selected spectral output and the desired wavelength dependentintensity distribution, and therefrom determining whether theillumination light contains the desired selected spectral output and thedesired wavelength dependent intensity distribution. The methods cancomprise adjusting the SLM to improve the correspondence between theillumination light and the desired selected spectral output and thedesired wavelength dependent intensity distribution. In still otheraspects, the present apparatus and methods comprise emitting modifiedlight consisting essentially of a desired selected spectral output and adesired wavelength dependent intensity distribution from a stand alonelight source.

The methods can further comprise directing the output beam to illuminatea material by at least one of directly illuminating the material via aprojected beam, or directing the beam into the light guide of aspectrometer, or other optical measurement system. The methods cancomprise capturing spectral measurement data such as spectroscopy dataof the light emitted by a material illuminated by the illumination lightfrom the CCIS and storing the spectroscopy data for processing, analysisor display in a computer memory.

The methods can further comprise illuminating a reference material withillumination light from the CCIS, and measuring the light returning fromit with an SMS and adjusting the light illuminating the referencematerial until a specific desired reference spectrum is obtained, suchas a flat line at the high end of a measurement scale for a referencewhite material, and storing the information about how the illuminationwas created to create a reference illumination data set. This can bereiterated to create a library of multiple reference illumination datasets, and/or modified to be specific to a desired material to create adesired material illumination data set.

The methods can further comprise comparing or otherwise analyzing orprocessing the desired material and the reference illumination data setsto derive information about the nature and amount of materials in thedesired material illumination data set.

The methods can further comprise illuminating a material with a sequenceof illumination patterns that can enhance the detection of thecharacteristics of a desired material of interest, for example, thecharacteristics of a range of explosive materials if the spectroscopydevice is an explosive detection device, or a range of impurities in achemical process analyzer. Such sequence can be implemented in a rapidfashion (i.e., many samplings per second). In some embodiments, theillumination patterns are characteristic of a material of interest butvary in intensity of response proportional to the concentration of thematerial of interest such that the concentration or amount of thematerial of interest present can be determined. The illuminationpatterns can also be characteristic of a mixture two or more materialsof interest but vary in intensity of response proportional to theconcentration of various mixtures of the material of interest such thatthe concentration or amount of the materials of interest present can bedetermined. The methods can further comprise combining sequences ofdigital or analog spectroscopy data and processing or combining them toform spectroscopy data of the material that provides useful information.

These and other aspects, features and embodiments are set forth withinthis application, including the following Detailed Description andattached drawings. The discussion herein provides a variety of aspects,features, and embodiments; such multiple aspects, features andembodiments can be combined and permuted in any desired manner. Inaddition, various references are set forth herein that discuss certainapparatus, systems, methods, or other information; all such referencesare incorporated herein by reference in their entirety and for all theirteachings and disclosures, regardless of where the references may appearin this application. Such incorporated references include: U.S. Pat. No.6,781,691; pending U.S. patent application Ser. No. 10/893,132, entitledApparatus And Methods Relating To Concentration And Shaping OfIllumination, filed Jul. 16, 2004; pending U.S. patent application Ser.No. 19/951,439 (attorney docket no. 1802-9-3), entitled Apparatus AndMethods Relating To Color Imaging Endoscope Systems, filedcontemporaneously herewith; pending U.S. patent application Ser. No.10/951,438, now U.S. Pat. No. 7,108,402 (attorney docket no. 1802-12-3),entitled Apparatus And Methods Relating To Precision

Control Of Illumination Exposure, filed contemporaneously herewith;pending U.S. patent application Ser. No. 10/951,448 (attorney docket no.1802-13-3), entitled Apparatus And Methods Relating To Expanded DynamicRange Imaging Endoscope Systems, filed contemporaneously herewith;pending U.S. patent application Ser. No. 10/951,449 (attorney docket no.1802-14-3), entitled Apparatus And Methods For Performing Phototherapy,Photodynamic Therapy And Diagnosis, filed contemporaneously herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A provides a schematic representation of a spectral measurementsystem, according to an embodiment of the invention, with a CCIS thatilluminates a target material and a spectral measurement sensor thatdetects light reflected by the target material.

FIG. 1B provides a schematic representation of a spectral measurementsystem, according to an embodiment of the invention, with a CCIS thatilluminates a target material with illumination light, and a detectorthat detects light transmitted by the target material.

FIG. 2 provides a schematic representation of an exemplary CCIS as shownin FIGS. 1A and 1B.

FIG. 3 provides schematic representations of light modified by a tunablelight source into illumination light having a broad spectral output witha substantially constant wavelength dependent intensity distribution (aflat spectrum), a narrow spectral output (a reduced bandwidth spectrum),or an arbitrary spectral output with an arbitrary wavelength dependentintensity distribution (an arbitrary spectrum).

FIG. 4 provides a schematic representation of illumination light havinga narrow spectral output with a substantially constant wavelengthdependent intensity distribution, and whose spectral output only variesin wavelength over time (swept over a broad range of wavelengths), andthe combined spectrum of the light emanating from a target materialgenerated by such illumination light, according to an embodiment of theinvention.

FIGS. 5A and 5B illustrate sequential spectral measurements. FIG. 5Aillustrates a case where successive measurements are made withsuccessively reduced intensity of the illumination light at selectedwavelengths. FIG. 5B illustrates a case where successive measurementsare made with different spectral shapes.

FIGS. 6A, 6B and 6C provide a schematic representation of dynamic rangeexpansion by a spectral measurement system herein that generates anduses illumination light having a narrow spectral output that is sweptover a broad range of wavelengths over time. FIG. 6A provides aschematic representation of the spectral measurement sensor 16 of thespectral measurement system being overexposed by certain wavelengths inthe broad range of wavelengths swept over time. FIG. 6B provides aschematic representation of reducing the wavelength dependent intensitydistribution of all the wavelengths in the broad range of wavelengthsswept over time, which results in effectively lowering the intensity ofcertain wavelengths of the light emanating from the target material.FIG. 6C provides a schematic representation of reducing the wavelengthdependent intensity distribution of certain wavelengths in the broadrange of wavelengths swept over time, which results in easily measurableintensities for all wavelengths of the light emanating from the targetmaterial.

FIGS. 7A, 7B and 7C provide a schematic representation of dynamic rangeexpansion by a spectral measurement system herein that generates anduses illumination light having a broad spectral output. FIG. 7A providesa schematic representation of the detection light sensor reachingsaturation for certain wavelengths in the spectral output of theillumination light. FIG. 7B provides a schematic representation ofreducing the wavelength dependent intensity distribution of all thewavelengths in the broad spectral output, which results in excessivelylowering the intensity of certain wavelengths of the light from thetarget material. FIG. 7C provides a schematic representation of reducingthe wavelength dependent intensity distribution of certain wavelengthsin the broad spectral output, which results in good intensities for allwavelengths of the light from the target material.

FIGS. 8A, 8B, 8C and 8D provide schematic representations of a sequenceof measurements involving a target material and a reference material.FIG. 8A illustrates illuminating the reference sample with illuminationlight comprising a broad spectrum of wavelengths and shows the resultantdetected spectrum. FIG. 8B illustrates illuminating the reference samplewith illumination light adjusted by reducing the intensity of certainwavelength such that the resultant detected spectrum is flat. FIG. 8Cillustrates the case where the adjusted light from FIG. 8B is used toilluminate a target sample, resulting in a detected spectrum that is nolonger flat and from which the target sample's spectrum can bedetermined. FIG. 8D illustrates the case where the illumination of thetarget same sample is adjusted so as to result in a flat detectedspectrum. The spectrum of the target sample can then be deduced from theadjusted illumination spectrum.

FIG. 9 is a flow chart depicting a power management scheme according tothe present invention.

DETAILED DESCRIPTION

The present apparatus and methods, etc., comprise spectral measurementsystems such as spectroscopy systems, spectroradiometry systems, orspectrophotometry systems to measure the spectral properties of amaterial such as gas, liquid, solid, chemical compound, biologicalmaterial such as biological fluids or tissue, paint or coating or othermaterial. The spectral measurement systems comprise acomputer-controlled illumination system (CCIS) that can generate andemit illumination light having a variable selected spectral output and avariable selected wavelength dependent intensity distribution anddirected toward the target material. The spectral measurement systemalso comprises an spectral measurement sensor (SMS) operably linked tothe CCIS and configured to detect light from the target material andgenerate spectral data representing at least the spectral distributionand wavelength dependent intensity distribution of the light from thetarget material. Furthermore, the spectral output and wavelengthdependent intensity distribution of the light generated by the CCIS maybe varied to correspond with different spectroscopic measurementtechniques.

For example, the spectral distribution and wavelength dependentintensity distribution of the illumination light may be varied so thatthe target material neither emits light, reflects light nor transmitslight when the target material receives the illumination light. Or, thespectral output and wavelength dependent intensity distribution of theillumination light may be varied so that the target material emits,reflects and/or transmits light having a spectral output with asubstantially constant wavelength dependent intensity distribution suchthat the intensity of emanation is substantially equal or flat acrossall desired wavelengths. For another example, the spectral distributionand wavelength dependent intensity distribution of the illuminationlight may be varied to enhance the dynamic range for the spectralmeasurement system. For yet another example, the spectral distributionand wavelength dependent intensity distribution of the illuminationlight may be varied to measure the different spectral properties of twoor more components of the target material. For still another example,the spectral distribution and wavelength dependent intensitydistribution of the illumination light may be varied so that the targetmaterial emits, reflects and/or transmits light having a spectral outputwith a substantially constant wavelength dependent intensitydistribution; and then the illumination light spectrum can be comparedto the illumination light spectrum of a reference material that producesa same substantially constant wavelength dependent intensitydistribution spectrum in light from the reference material.

Turning to some general information about light, the energy distributionof light is what determines the nature of its interaction with anobject, compound or organism. A common way to determine the energydistribution of light is to measure the amount or intensity of light atvarious wavelengths to determine the energy distribution or spectrum ofthe light. To make light from a light source useful for a particularpurpose it can be conditioned to remove undesirable wavelengths orintensities, or to enhance the relative amount of desirable wavelengthsor intensities of light. For example, a high signal-to-noise ratio andhigh out-of-band rejection enhances the spectral characteristics oflight.

The systems and methods herein, including kits and the like comprisingthe systems or for making or implementing the systems or methods,provide the ability to selectively, and variably, decide which colors,or wavelengths, of light will be projected from the system, and howstrong each of the wavelengths will be. The wavelengths can be a singlewavelength, a single band of wavelengths, a group ofwavelengths/wavelength bands, or all the wavelengths in a light beam. Ifthe light comprises a group of wavelengths/wavelengths bands, the groupcan be either continuous or discontinuous. The wavelengths can beattenuated so that the relative level of one wavelength to another canbe increased or decreased (e.g., decreasing the intensity of onewavelength among a group of wavelengths effectively increases the otherwavelengths relative to the decreased wavelength). This is advantageousbecause such fine control of spectral output and wavelength dependantintensity distribution permits a single illumination system to providehighly specialized illumination light for spectroscopy.

Definitions.

The following paragraphs provide definitions of some of the terms usedherein. All terms used herein, including those specifically describedbelow in this section, are used in accordance with their ordinarymeanings unless the context or definition indicates otherwise. Alsounless indicated otherwise, except within the claims, the use of “or”includes “and” and vice-versa. Non-limiting terms are not to beconstrued as limiting unless expressly stated (for example, “including”and “comprising” mean “including without limitation” unless expresslystated otherwise).

A “controller” is a device that is capable of controlling a spatiallight modulator, a detector or other elements of the apparatus andmethods herein. A “controller” contains or is linked tocomputer-implemented programming. Typically, a controller comprises oneor more computers or other devices comprising a central processing unit(CPU) and directs other devices to perform certain functions or actions,such as the on/off pattern of the pixels in the pixelated SLM, theon/off status of pixels of a pixelated light detector (such as a chargecoupled device (CCD) or charge injection device (CID)), and/or compiledata obtained from the detector, including using such data to make orreconstruct images or as feedback to control an upstream spatial lightmodulator. A computer comprises an electronic device that can storecoded data and can be set or programmed to perform mathematical orlogical operations at high speed. Controllers are well known andselection of a desirable controller for a particular aspect of thepresent apparatus and methods is within the scope of the art in view ofthe present disclosure.

A “spatial light modulator” (SLM) is a device that is able toselectively modulate light. The present apparatus and methods compriseone or more spatial light modulators disposed in the light path of anillumination system. A pixelated spatial light modulator comprises anarray of individual pixels, which are a plurality of spots that havelight passing characteristics such that they transmit, reflect orotherwise send light along a light path, or instead block the light andprevent it or interrupt it from continuing along the light path. Suchpixelated arrays are well known, having also been referred to as amultiple pattern aperture array, and can be formed by an array offerroelectric liquid crystal devices, electrophoretic displays, or byelectrostatic microshutters. See, U.S. Pat. No. 5,587,832; U.S. Pat. No.5,121,239; R. Vuelleumier, Novel Electromechanical Microshutter DisplayDevice, Proc. Eurodisplay '84, Display Research Conference September1984.

A reflective pixelated SLM comprises an array of highly reflectivemirrors that are switchable been at least two different angles ofreflection. One example of a reflective pixelated SLM is a digitalmicromirror device (DMD), as well as other MicroElectroMechanicalStructures (MEMS). DMDs can be obtained from Texas Instruments, Inc.,Dallas, Tex., U.S.A. In this embodiment, the mirrors have three states.In a parked or “0” state, the mirrors parallel the plane of the array,reflecting orthogonal light straight back from the array. In oneenergized state, or a “−10” state, the mirrors fix at −10° relative tothe plane of the array. In a second energized state, or a “+10” state,the mirrors fix at +10° relative to the plane of the array. Other anglesof displacement are possible and are available in different models ofthis device. When a mirror is in the “on” position light that strikesthat mirror is directed into the illumination light path. When themirror is in the “off” position light is directed away from theillumination light path. On and off can be selected to correspond toenergized or non-energized states, or on and off can be selected tocorrespond to different energized states. If desired, the light directedaway from the projection light path can also be collected and used forany desired purpose (in other words, the DMD can simultaneously orserially provide two or more useful light paths). The pattern in the DMDcan be configured to produce two or more spectral and intensitydistributions simultaneously or serially, and different portions of theDMD can be used to project or image along two or more differentprojection light paths.

A “spectrum former” can be any desired optical and/or electrical elementthat separates a light beam into its respective spectral components,such as a prism, a diffraction grating, either planar or curved, such asa reflective diffraction grating or a transmission diffraction grating,an optical filter comprising a linearly variable wavelength filter orother spatially variable wavelength filter, or a mosaic optical filter.A linearly variable wavelength filter is an optical filter where thewavelength that is transmitted varies across the face of the filter,such as filters made by OCLI, a JDS Uniphase company, where thewavelength of transmission varies in a continuous manner betweenpositions of incident light from one end of the filter to the other end.This filter can be linearly variable, non-linearly variable or step-wisevariable.

An “illumination light path” is the light path from a light source to atarget or scene, while a “detection light path” is the light path forlight emanating from a sample (e.g., light reflecting from a sample,emitting (e.g., fluorescing) from a sample, transmitted through asample), to a detector. The light includes ultraviolet (UV) light, bluelight, visible light, near-infrared (NIR) light and infrared (IR) light.

“Upstream” and “downstream” are used in their traditional sense whereinupstream indicates that a given device is closer to a light source,while downstream indicates that a given object is farther away from alight source.

The scope of the present apparatus and methods includes both means plusfunction and step plus function concepts. However, the terms set forthin this application are not to be interpreted in the claims asindicating a “means plus function” relationship unless the word “means”is specifically recited in a claim, and are to be interpreted in theclaims as indicating a “means plus function” relationship where the word“means” is specifically recited in a claim. Similarly, the terms setforth in this application are not to be interpreted in method or processclaims as indicating a “step plus function” relationship unless the word“step” is specifically recited in the claims, and are to be interpretedin the claims as indicating a “step plus function” relationship wherethe word “step” is specifically recited in a claim.

Other terms and phrases in this application are defined in accordancewith the above definitions, and in other portions of this application.

FIGS. 1A and 1B provide schematic representations of a spectralmeasurement system 10, according to an embodiment of the invention. Thespectral measurement system 10 comprises a CCIS 12 that generates andemits illumination light 14, and a spectral measurement sensor 16configured to detect emanating light 18 from a target material 20. Theillumination light 14 comprises a spectral output and wavelengthdependent intensity distribution that may be varied as desired, and isdirected toward the target material 20. The target material 20 receivesthe illumination light 14 and absorbs all or a portion the illuminationlight 14, reflects (FIG. 1A) all or a portion of the illumination light14, transmits (FIG. 1B) all or a portion of the illumination light 14,and emits light (not shown), to generate the emanating light 18 from thetarget material, or otherwise interacts with the illumination light. Thespectral measurement sensor 16 then detects the emanating light 18 andgenerates data representing at least the spectral distribution andwavelength dependent intensity distribution of the emanating light 18.In some embodiments, The spectral measurement system 10 comprises atleast one of a data capture device and a data acquisition and processingdevice. The data capture device is operable to record data from at leastone of the computer-controlled illumination device 12 and the spectralmeasurement sensor 16, for future use as desired. The data acquisitionand processing device is operable to analyze data from at least one ofthe computer-controlled illumination device 12 and the spectralmeasurement sensor 16, for use as desired. The data capture device and adata acquisition and processing device can, for example, be a part ofthe spectral measurement computer 16 or a part of the controller 24depicted in FIG. 2.

FIG. 2 provides a schematic representation of a CCIS 12 according to anembodiment of the invention. The CCIS 12 comprises a tunable lightsource 22 for generating and emitting the illumination light 14, and acontroller 24 for varying the spectral output and wavelength dependentintensity distribution of the illumination light 14 to provide a desiredillumination light 14.

The tunable light source 22 provides virtually any desired color(s) andintensity(s) of light, from white light, or light that is visible to anunaided human eye, to light containing only a certain color(s) andintensity(s). The colors, or “spectral output,” which means a particularwavelength, band of wavelengths, or set of wavelengths, as well as theintensities, which means a “wavelength dependent intensitydistribution,” can be combined and varied as desired. The tunable lightsource may also provide other kinds of light, such as UV light andinfrared light.

The tunable light source 22 comprises a light source 26 to generatelight 28, and a tunable filter 30 to generate a desired spectral outputand wavelength dependent intensity distribution. The tunable filter 30may be any desired device capable of modulating the light 28 from thelight source 26. For example, the tunable filter 30 may comprise aspectrum former 32 to separate the light 28 into its spectral components34, and a pixelated SLM 36 to combine selected spectral components togenerate the illumination light 14 having the desired spectral outputand wavelength dependent intensity distribution, and to separateunwanted spectral components 38 from the selected spectral components.By selectively turning on or off individual pixels of the pixelated SLM36, one can generate illumination light 14 having a desired spectraloutput and a desired wavelength dependent intensity distribution. Forexample, only one narrow wavelength of light from the spectralcomponents 34, such as only a pure green line of light in a typicallinear spectrum may be generated, or non-linear spectra can begenerated. By varying the duty cycle of some of the pixels to be turnedon or off, virtually any spectral distribution of light can be created.The pixelated SLM 36 may be transmissive or reflective. In otherembodiments, the tunable filter may comprise an acousto-optic tunablefilter, LCOS, or other desired tunable device. Suitable tunable lightsources are discussed, e.g., in U.S. Pat. No. 6,781,691 and U.S. patentapplication Ser. No. 10/893,132.

In some embodiments, the CCIS 12 can comprise an illumination-lightdetector 40 for detecting the illumination light 14 and transmittingdata representing the spectral output and wavelength depended intensitydistribution of the illumination light 14 to the controller 24. Theillumination-light detector 40 may be any desired device capable ofsensing the illumination light 14 and generating data representing thespectral distribution and wavelength dependent intensity distribution ofthe illumination light 14. For example, the illumination-light detector40 may comprise a spectrometer, a spectroradiometer, a charge coupleddevice (CCD), a charge injection device (CID), a complementarymetal-oxide semi-conductor (CMOS), and a photodiode array. In someembodiments, the illumination-light detector 40 receives illuminationlight 14 from a beam splitter such as lens 42 so that the illuminationlight 14 projected toward the target material is not affected by thesensor 40.

The controller 24 includes computer-implemented programming to instructthe tunable light source 22 to vary the spectral output and wavelengthdependent intensity distribution of the illumination light 14. In someembodiments, the controller can be operably connected to at least one ofthe spectral measurement sensor 16 (FIGS. 1A and 1B) and theillumination-light detector 40, and can coordinate one or both of thesensors 16 and 40 with the tunable light source 22 to vary the spectraloutput and wavelength dependent intensity distribution of theillumination light 14. Such coordination with the spectral measurementsensor 16 typically comprises receiving the data generated by thespectral measurement sensor 16 and varying the spectral output and/orwavelength dependent intensity distribution to perform one or moredifferent spectroscopic measurement techniques (discussed in greaterdetail in conjunction with FIGS. 3-8D). Such coordination with thesensor 40 typically comprises determining whether the spectral outputand wavelength dependent intensity distribution of the illuminationlight 14 is the selected spectral output and wavelength dependentintensity distribution, and varying the spectral output and/orwavelength dependent intensity distribution of the illumination light 14as desired. In some embodiments, the controller 24 is operably connectedto the SLM 36, and the computer-implemented programming controls theon/off pattern of the pixels. Suitable controllers are discussed, e.g.,in U.S. Pat. No. 6,781,691 and U.S. patent application Ser. No.10/893,132.

In some embodiments, the controller 24 can comprise at least one of adata capture device and the data acquisition and processing device. Withthe processed data, the controller 24 can generate an image such as adigital image to be displayed for any desired reason, such as monitoringthe progress of the spectroscopic measurement or evaluation by a humanoperator. Furthermore, the controller 24 may use the processed data todetermine whether to vary the spectral output, the wavelength dependentintensity distribution or both, of the illumination light generated bythe CCIS 12, and if so, then to what degree.

The CCIS 12 may comprise other components as desired. For example, theCCIS 12 may comprise at least one of a projection system to project theillumination light 14 toward the target material 20, and a heatmanagement system to remove undesired energy generated by the tunablelight source 22. The projection system may be desirable to enlarge,decrease or change the geometric form of the coverage area of theillumination light 14 on the target material 20 area and may compriseany desired optical device to accomplish this. For example, theprojection system may include lenses and may focus the illuminationlight 14 onto an area of the target material 20 that is less than thecoverage area would be without the projection system; or the projectionsystem may disperse the illumination light onto an area of the targetmaterial 20 that is more than the coverage area would be without theprojection system; and/or the projection system may modify theillumination light 14 to project the illumination light 14 in a formthat corresponds to the form of a region of the target material to beilluminated, such as a long, narrow region corresponding to arectangular sample. The heat management system may comprise any desiredcomponent or assembly of components and may be configured relative tothe tunable light source 22 to remove undesired energy emitted from thelight source 26. For example, the heat management system may comprise anenergy-absorbing surface, preferably one thermally connected tothermally conduct the heat to a radiator, or an optical cell containinga liquid that absorbs undesired wavelengths and transmits desiredwavelengths, such as water. For embodiments where the heat managementsystem comprises an optical cell, the optical cell can also comprise aninlet port and an outlet port so that fresh liquid can be provided, andif desired the liquid can flow in a re-circulating path between theoptical cell and a reservoir. The re-circulating path or the reservoircan further comprise a cooling device such as a refrigeration unit, athermal-electric cooler and a heat exchanger. Suitable projection andheat management systems are discussed, e.g., in U.S. Pat. No. 6,781,691and U.S. patent application Ser. No. 10/893,132.

Because the computer-controlled illumination system 12 can provide anillumination light 14 having a desired spectral output and wavelengthdependent intensity distribution, and can vary the spectral output andwavelength dependent intensity distribution as desired, the spectralmeasurement system 10 may be easily used to perform a variety ofspectroscopic measurement techniques. For example, the spectraldistribution and wavelength dependent intensity distribution of theillumination light 14 may be varied so that the target material neitheremits emanating light 18

(FIGS. 1A and 1B) reflects emanating light 18 nor transmits emanatinglight 18 when the target material 20 receives the illumination light 14.Or, the spectral output and wavelength dependent intensity distributionof the illumination light 14 may be varied so that the target materialemits, reflects and/or transmits emanating light 18 having a spectraloutput with a substantially constant wavelength dependent intensitydistribution. For another example, the spectral distribution andwavelength dependent intensity distribution of the illumination light 14may be varied to enhance the dynamic range for the spectral measurementsystem 10. For yet another example, the spectral distribution andwavelength dependent intensity distribution of the illumination light 14may be varied to measure the different spectral properties of two ormore components of the target material 20. For still another example,the spectral distribution and wavelength dependent intensitydistribution of the illumination light 14 may be varied so that thetarget material 20 emits, reflects and/or transmits emanating light 18having a spectral output with a substantially constant wavelengthdependent intensity distribution; and then the illumination lightspectrum can be compared to the illumination light spectrum of areference material that produces a same substantially constantwavelength dependent intensity distribution spectrum in light from thereference material.

FIG. 3 provides a schematic representation of light 28 (FIG. 2) modifiedby a tunable light source 22 (FIG. 2) into illumination light 14 (FIGS.1A-2) having any desired spectral output and wavelength dependentintensity distribution. For example, the spectral output and wavelengthdependent intensity distribution of the illumination light 14 cancomprise the spectrum 50. The spectrum 50 can be generated from thespectrum 52 of the light 22 from the light source 26 (FIG. 2) and caninclude a broad spectral output with a substantially constant wavelengthdependent intensity distribution. Or, the spectral output and wavelengthdependent intensity distribution of the illumination light 14 cancomprise the spectrum 54, which can be generated from the spectrum 52and can include a narrow spectral output. Or, the spectral output andwavelength dependent intensity distribution of the illumination light 14can comprise the spectrum 56, which can be generated from the spectrum52 and can include an arbitrary spectral output with an arbitrarywavelength dependent intensity distribution.

Because the CCIS 12 can generate illumination light 14 having aninfinite variety of spectral outputs and wavelength dependent intensitydistributions, the spectral measurement system 10 (FIGS. 1A and 1B) maybe easily adapted for efficiently measuring the spectral properties ofmany different target materials.

FIG. 4 provides a schematic representation of illumination light 14(FIGS. 1A-2) that is generated by sequencing or sweeping a narrowspectral output with a substantially constant wavelength dependentintensity distribution over a range of wavelengths over time, accordingto an embodiment of the invention. For example, at a first instant, thetunable light source 22 may generate a spectrum 58 of illumination light14 having a wavelength spectral output of approximately 425-450nanometers. Then at a second instant, which may be any duration of timeafter the first instant including as few as 1 millisecond, the tunablelight source 22 may generate a spectrum of illumination light 14 havinga wavelength spectral output of approximately 450-475nanometers. Afterthe narrow spectral output with a substantially constant wavelengthdependent intensity distribution has swept through the desired range ofwavelengths, the individual spectra of the emanating light 18 (FIGS. 1Aand 1B) from the target material 20 (FIGS. 1A and 1B) that correspondwith each sequential spectrum of illumination light are combined to makethe spectrum 59.

In other embodiments, the sequencing or sweeping the narrow spectraloutput with a substantially constant wavelength dependent intensitydistribution over a range of wavelengths over time can be repeated overthe same or a different range of wavelengths. Repeating the sequencingor sweeping may be desirable to measure the change of a targetmaterial's spectral properties over time and/or measure differentoptical characteristics of the target material's spectral property,which may be used to determine different components of the targetmaterial 20.

FIG. 5 a provides a schematic representation of illumination light 14(FIGS. 1A-2) having a spectral output and wavelength dependent intensitydistribution, and whose spectral output only varies in wavelengthdependent intensity distribution over time, according to an embodimentof the invention. Each of the spectra 60, 61, 62 represent illuminationlight 14 having substantially the same spectral output but differentwavelength dependent intensity distributions. Varying only thewavelength dependent intensity distribution of the illumination light 14may be desirable when the spectral properties of the target material 20are more responsive to changes in the wavelength dependent intensitydistribution of a spectral output having a broad range than to a narrowspectral output. FIG. 5 b provides a schematic representation ofillumination light 14 (FIGS. 1A-2) having a substantially differentspectral output and a substantially different wavelength dependentintensity distribution, as shown in graphs 64, 65 and 66.

FIGS. 6A, 6B and 6C provide a schematic representation of dynamic rangeexpansion for the spectral measurement system 10 (FIGS. 1A and 1B)according to an embodiment of the invention, that generates and usesillumination light having a narrow spectral output that is swept over abroad range of wavelengths over time.

Dynamic range expansion is a process of varying the wavelength dependentintensity distribution of a portion of the spectral output of theillumination light 14 (FIGS. 1A-2) to compensate for overexposing and/orunderexposing the spectral measurement sensor 16 (FIGS. 1A and 1B).Overexposure and underexposure is somewhat like overexposing orunderexposing a picture taken with a normal camera, and means that themeasurement generated from the data generated by the spectralmeasurement sensor 16 does not accurately represent the spectralproperty of the target material. Previously, overexposure andunderexposure have been corrected by increasing or decreasing theintensity of all the wavelengths in the illumination light directedtoward a target material. But because overexposure and underexposure isoften due to a single or few wavelengths in the spectrum of illuminationlight, increasing or decreasing the intensity of all the wavelengths inthe illumination light frequently detrimentally reduces or increases theintensity of certain wavelengths in the illumination light that did notcause the overexposure and/or underexposure. Thus, the accuracy of thedisplayed spectral property of the target material 20 (FIGS. 1A and 1B)may be adversely affected.

With the tunable light source 22, the wavelength dependent intensitydistribution of the portion of the spectral output causing theoverexposure and/or underexposure can be increased or decreased asdesired without increasing or decreasing the wavelength dependentintensity distribution of the remaining portions of the spectral output.Consequently, the dynamic range of the spectral measurement system 10(FIGS. 1A and 1B) may be expanded to provide a more accurate measurementof the target material's spectral property. Expanding the dynamic rangeof a sensor is further discussed, e.g., in U.S. provisional patentapplication 60/506,273 titled Apparatus And Methods Relating To ExpandedDynamic Range Imaging Endoscope Systems and filed Sep. 26, 2003, andU.S. patent application Ser. No. 10/951,448, titled Apparatus AndMethods Relating To Expanded Dynamic Range Imaging Endoscope Systems andfiled Sep. 27, 2004 (attorney docket numbers 1802-013-02 and1802-013-03).

FIG. 6A provides a schematic representation of the spectral measurementsensor 16 of the spectral measurement system 10 being overexposed bycertain wavelengths in the broad range of wavelengths swept over time.The tunable light source 22 (FIG. 2) can generate illumination light 14,as discussed in conjunction with FIG. 4, that comprises the spectrum 68.The individual spectra of the emanating light 18 (FIGS. 1A and 1B) fromthe target material 20 that correspond with each sequential spectrum ofillumination light 14 are combined to make the spectrum 70. The spectrum70 includes wavelengths that would overexpose the spectral measurementsensor 16, for example the range of wavelengths comprising wavelengthsabout 550 nanometers to 600 nanometers.

FIG. 6B provides a schematic representation of the illumination light 14schematically depicted in FIG. 6A after the wavelength dependentintensity distribution of all the wavelengths in the broad range ofwavelengths swept over time, have been reduced. Consequently, theillumination light comprises the spectrum 72, and the individual spectraof the emanating light 18 from the target material 20 that correspondwith each sequential spectrum of illumination light 14 are combined tomake the spectrum 74. By reducing the wavelength dependent intensitydistribution of all the wavelengths in the broad spectrum, the spectrum74 includes wavelengths whose intensities may be so low that the sensor16 cannot accurately detect them. Thus the measurement of the targetmaterial's spectral property may be inaccurate.

FIG. 6C provides a schematic representation of the illumination light 14schematically depicted in FIG. 6A after the wavelength dependentintensity distribution of a portion of the broad range wavelengths sweptover time, has been selectively reduced. Consequently, the illuminationlight comprises the spectra 76, 78 and 80, and the individual spectra ofthe emanating light 18 from the target material 20 that correspond witheach sequential spectrum of illumination light 14 are combined to makethe spectrum 82. By reducing the wavelength dependent intensitydistribution of only the wavelengths in the broad spectrum that causethe overexposure of the spectral measurement sensor 16, substantiallyall of the wavelengths in the spectrum 82 have an intensity thatcorresponds with the sensor's optimal range for sensitivity. Thus themeasurement of the target material's spectral property may be asaccurate as the sensor will permit.

FIGS. 7A, 7B and 7C provide a schematic representation of dynamic rangeexpansion for the spectral measurement system 10 (FIGS. 1A and 1B)according to an embodiment of the invention that generates and usesillumination light 14 (FIGS. 1A-2) having a broad spectral output. Theschematic representations of expanding the dynamic range of the spectralmeasurement system 10 that are depicted in FIGS. 7A-7C are similar tothe schematic representations of expanding the dynamic range of thesystem 10 that are depicted in FIGS. 6A-6C. The primary differencebetween the dynamic range expansions depicted in FIGS. 7A-7C and 6A-6Cis that the process for generating the illumination light 14 isdifferent.

FIG. 7A provides a schematic representation of the spectral measurementsensor 16 of the spectral measurement system 10 being overexposed bycertain wavelengths in the spectral output of the illumination light 14.The spectrum 84 represents the spectral output and wavelength intensitydistribution of the illumination light 14, and the spectrum 86represents the range of wavelengths and respective intensities of theemanating light 18 (FIGS. 1A and 1B) from the target material 20 afterthe target material 20 receives the illumination light 14 represented bythe spectrum 84.

FIG. 7B provides a schematic representation of the illumination light 14schematically depicted in FIG. 7A after the wavelength dependentintensity distribution of all the wavelengths in the spectral outputhave been reduced. The spectrum 88 represents the spectral output andwavelength intensity distribution of the illumination light 14, and thespectrum 90 represents the range of wavelengths and respectiveintensities of the emanating light 18 from the target material 20 afterthe target material 20 receives the illumination light 14 represented bythe spectrum 88.

FIG. 7C provides a schematic representation of the illumination light 14schematically depicted in FIG. 7A after the wavelength dependentintensity distribution of a portion of the spectral output have beenreduced. The spectrum 92 represents the spectral output and wavelengthintensity distribution of the illumination light 14, and the spectrum 94represents the range of wavelengths and respective intensities of theemanating light 18 from the target material 20 after the target material20 receives the illumination light 14 represented by the spectrum 92.

FIGS. 8A, 8B, 8C and 8D provide a schematic representation of aplurality of measurements involving a known reference target material 96and an unknown target material 20 (FIGS. 1A-2). By knowing the referencetarget material 96 and the spectral output and wavelength dependentintensity distribution of the illumination light 14 (FIGS. 1A and 1B)that produces a certain spectral output and wavelength dependentintensity distribution in the emanating light 18 (FIGS. 1A and 1B) fromthe known reference target material 96 after it receives theillumination light 14, one can determine the unknown target materialfrom the spectral output and wavelength dependent intensity distributionby using a same illumination light 14 that produces the same orsubstantially the same emanating light 18.

The known reference target material 96 may or may not be the samematerial as the unknown target material 20. If the known referencetarget material and the unknown target material are the same, then theirspectral outputs and wavelength dependent intensity distributions fromsubstantially identical illumination light will be substantially thesame. If, however, the known reference target material and the unknowntarget material are not the same, then determining the unknown targetmaterial can comprise, for example, illuminating them with identicalillumination light then comparing the resulting spectra emanating fromthe samples, or illuminating them with different illumination lightconfigured to generate the same or substantially the same emanatinglight and then analyzing the similarities or differences of theillumination light. The same or substantially the same spectral outputand wavelength dependent intensity distribution of the emanating light18 from the known reference target material 96 and unknown targetmaterial 20 may comprise, for example, an absence of light (even thoughthe illumination light has substantial intensity, i.e., the targetmaterials 20 and 96 neither emit, reflect or transmit emanating light18), a spectral output having a substantially constant wavelengthdependent intensity distribution (e.g., FIGS. 8B and 8D). In otherembodiments, differing illumination light differing a spectral outputhaving a varied wavelength dependent intensity distribution are usedwith computer programs that compare and contrast various differences andsimilarities in the lights to determine one or two or more likelymatches.

FIGS. 8A and 8B provide a schematic representation of generating areference illumination data set, which comprises data corresponding tothe material of the reference target material 96, data corresponding tothe certain spectral output and wavelength dependent intensitydistribution in the emanating light 18 a, and data corresponding to thespectral output and wavelength dependent intensity distribution of theillumination light 14 a. In some embodiments, two or more referenceillumination data sets may comprise a library of data sets. Each dataset in the library may be generated under substantially the sameconditions, for example the reference target materials 96 and certainspectral output and wavelength dependent intensity distribution in eachdata set may be substantially the same. This may be desirable to providea composite data set that provides an average of the data values for amore accurate comparison. In other embodiments, each data set in thelibrary may be generated under different conditions, for example thereference target material 96 may change relative to each data set and/orthe certain spectral output and wavelength dependent intensitydistribution may change relative to each data set. This may be desirableto provide a reference material that could closely match the unknowntarget material.

FIG. 8A provides a schematic representation of the step of detecting thespectral distribution and wavelength dependent intensity distribution ofemanating light 18 b from the known reference target material 96. Thetunable light source 22 (FIG. 2) generates illumination light 14 b thatcomprises the spectrum 98. The spectral measurement sensor 16 (FIGS. 1Aand 1B) detects the emanating light 18 b that comprises the spectrum 100after the known reference target material 96 receives the illuminationlight 14 b.

FIG. 8B provides a schematic representation of the next step of varyingthe spectral output and wavelength dependent intensity distribution ofthe illumination light 14 a to produce emanating light 18 a from thereference material that has a substantially constant intensitythroughout the light's spectrum. The tunable light source 22 varies theillumination light to generate illumination light 14 a that results inspectrum 102. The spectral measurement sensor 16 detects the emanatinglight 18 a that comprises the spectrum 104 after the known referencetarget material 96 receives the illumination light 14 a. The spectrum104 comprises a spectral output having a substantially constantwavelength dependent intensity distribution.

FIGS. 8C and 8D provide schematic representations of generating anillumination light 14 c to produce a emanating light 18 c from theunknown target material 20 having the same or substantially the samespectral distribution wavelength dependent intensity distribution as theemanating light 18 a (FIG. 8B).

FIG. 8C provides a schematic representation of the step of detecting thespectral distribution and wavelength dependent intensity distribution ofemanating light 18 from the unknown target material 20. The tunablelight source 22 (FIG. 2) generates illumination light 14 d thatcomprises the spectrum 106. In the embodiment shown, the illuminationlight 14 d and the spectrum 106 are substantially identical to theillumination light 14 a and the spectrum 102. If the target sample 20were the same as reference sample 96, then the spectrum 108 would besubstantially identical to spectrum 104. In the embodiment shown,however, the target sample is different from reference sample 96 so adifferent spectrum 108 is obtained. The spectral measurement sensor 16(FIGS. 1A and 1B) detects the emanating light 18 d that comprises thespectrum 108 after the known reference target material 96 receives theillumination light 14 b.

FIG. 8D provides a schematic representation of a next step comprisingusing the tunable light source 22 to vary the spectral output andwavelength dependent intensity distribution of the illumination light toproduce illumination light 14 c having spectrum 110 that produces asubstantially constant intensity emanating light 18 c across thespectrum from the unknown target material 20. The spectral measurementsensor 16 detects the emanating light 18 c that comprises the spectrum112 after the unknown target material 20 receives the illumination light14 c. The spectrum 112 comprises a spectral output having asubstantially constant wavelength dependent intensity distribution asthe spectrum 104 (FIG. 8B).

In some aspects, the present invention includes light engines andmethods related thereto as discussed herein comprising specific, tunablelight sources, which can be digital or non-digital. As noted elsewhereherein, one aspect of these systems and methods relates to the abilityof the engines to provide finely tuned, variable wavelength ranges thatcorrespond to precisely desired wavelength patterns, such as, forexample, noon in Sydney Australia on October 14^(th) under a cloudlesssky, or medically useful light of precisely 442 nm. For example, suchspectra are created by receiving a dispersed spectrum of light from atypically broad spectrum light source (narrower spectrum light sourcescan be used for certain embodiments if desired) such that desiredwavelengths and wavelength intensities across the spectrum can beselected by the digital light processor to provide the desired intensitydistributions of the wavelengths of light. The remaining light from theoriginal light source(s) is then shunted off to a heat sink, light sinkor otherwise disposed of (in some instances, the unused light can itselfbe used as an additional light source, for metering of the emanatinglight, etc.).

In the present invention, either or both the light shunted to the heatsink or the light delivered to the target, or other light as desired, ismeasured. If the light is/includes the light to the light sink, then themeasurement can, if desired, include a comparison integration of themeasured light with the spectral distribution from the light source todetermine the light projected from the light engine. For example, thelight from the light sink can be subtracted from the light from thelight source to provide by implication the light sent to a target. Thelight source is then turned up or down, as appropriate, so that as muchlight as desired is provided to the target, while no more light thandesired, and no more power than desired, is emanated from or used by thelight source. In the past, it was often undesirable to reduce orincrease the power input/output of a given light source because it wouldchange the wavelength profile of the light source. In the present systemand methods, this is not an issue because the altered wavelength outputof the light source is detected and the digital light processor ismodified to adapt thereto so that the light ultimately projected to thetarget continues to be the desired wavelength intensity distribution.

This aspect is depicted in a flow chart, FIG. 9, as follows: Is thewavelength intensity distribution across the spectrum correct? If yes,then proceed with the analysis; if no, then revise the wavelengthintensity distribution across the spectrum as desired. Is the intensitytarget light distribution adequate? If no, then increase power outputfrom light source and repeat. If yes, then proceed to next step. Isthere excess light (for example being delivered to the light sink)? Ifyes, then decrease power to/from the light source. If no, then deemacceptable and leave as is. If power is increased or decreased: Re-checkspectral distribution (e.g., of light emanated to target and/or of lightfrom light power source) and if it is changed, reconfigure the digitallight processor to adapt to the changed spectral input. If the lightengine is changed, then reassess if light source can be turned up ordown again. Repeat as necessary.

Some other advantages to the various embodiments herein is that thesystem is more power friendly, produces less heat, thereby possiblyrequiring fewer or less robust parts, and in addition should assist inincreasing the longevity of various parts of the system due, forexample, to the reduced heat generated and the reduced electricitytransmitted and the reduced light transmitted. At the same time, thiswill provide the ability to use particular energy-favorable lightsources that might not otherwise be able to be used due to fears overchanged spectral distributions due to increased or decreased poweroutput at the light source.

From the foregoing, it will be appreciated that, although specificembodiments of the apparatus and methods have been described herein forpurposes of illustration, various modifications may be made withoutdeviating from the spirit and scope of the apparatus and methods.Accordingly, the apparatus and methods include such modifications aswell as all permutations and combinations of the subject matter setforth herein and are not limited except as by the appended claims.

1-23. (canceled)
 24. A method for measuring spectral properties of atarget material, the method comprising: generating an illumination lightcontaining a desired variable spectral output and desired variablewavelength dependent intensity distribution from a computer-controlledillumination system comprising a tunable light source configured to emitthe illumination light and a controller operably connected to thetunable light source and configured to vary the desired spectral outputand desired wavelength dependent intensity distribution of theillumination light to provide the desired spectral output and desiredwavelength dependent intensity distribution ; directing the illuminationlight toward the target material; sensing the light from the target witha spectral measurement sensor; determining target spectral data thatrepresents at least a spectral distribution and wavelength dependentintensity distribution of light emanating from the target material; andtransmitting the target spectral data to the controller, wherein thecontroller receives the target spectral data and incorporates the targetspectral data to tune the tunable light source.
 25. The method of claim24 further comprising detecting light reflecting from the targetmaterial.
 26. The method of claim 24 or 25 further comprising detectinglight transmitted through the target material.
 27. The method of claim24 further comprising detecting light emitting from the target material.28. The method of claim 24 wherein the illumination light comprises atleast two of infrared light, ultraviolet light or visible light.
 29. Themethod of claim 24 wherein generating the illumination light comprises:emitting light from a light source, passing the light by a spectrumformer optically connected to and downstream from the light source toprovide a spectrum from the light emitted from the light source, andpassing the spectrum via a pixelated spatial light modulator (SLM)located downstream from and optically connected to the spectrum former,the pixelated SLM configured to pass substantially only the desiredspectral output and wavelength dependent intensity distribution of thelight from the source to provide the illumination light.
 30. The methodof claim 29 wherein passing the spectrum via the pixelated SLM comprisesreflecting the spectrum off the SLM to provide the desired spectraloutput and wavelength dependent intensity distribution of theillumination light.
 31. The method of claim 29 or 30 wherein passing thespectrum via the pixelated SLM comprises controlling an on/off patternof pixels in the pixelated SLM with computer-implemented programmingcontained in the controller, to pass substantially only the spectraloutput and wavelength dependent intensity distribution of illuminationlight.
 32. The method of claim 24 further comprising varying theselected spectral output and wavelength dependent intensity distributionof the illumination light to illuminate the target material with anarrow wavelength band illumination light that sweeps through a desiredportion of the light spectrum.
 33. The method of claim 24 wherein themethod further comprises varying the selected spectral output andwavelength dependent intensity distribution of the illumination light inresponse to the target spectral data to evoke a substantially flatintensity of light emanating from the target material across all desireddetected wavelengths, the substantially flat intensity of light beingsubstantially greater than zero, and determining from the varying thespectral properties of the target material.
 34. The method of claim 24wherein generating the illumination light comprises generating at leasttwo different types of illumination light in sequence, wherein one ofthe types comprises a spectral output and wavelength dependent intensitydistribution for measuring a first spectral characteristic of the targetmaterial, and a second type comprises a spectral output and wavelengthdependent intensity distribution for measuring a second spectralcharacteristic of the target material.
 35. The method of claim 24wherein generating the illumination light comprises generatingillumination light that remains substantially the same over time and themethod further comprises measuring changes in spectral characteristicsof the target material over time.
 36. The method of claim 24 whereingenerating the illumination light comprises varying the illuminationlight to compensate for over-saturation or underexposure of the spectralmeasurement sensor in a specific wavelength range but withoutsubstantially changing the illumination light in acceptable wavelengthdistributions, thereby enhancing the dynamic range of the systemrelative to the spectral measurement sensor alone.
 37. The method ofclaim 24 further comprising comparing the target spectral data toreference spectral data of at least one known reference material: 38.The method of claim 37 wherein the method further comprises comparingthe target spectral data to reference spectral data of a plurality ofknown reference materials, and determining whether the target spectraldata substantially matches a matching reference spectral data.
 39. Themethod of claim 38 wherein the method further comprises comparing thetarget spectral data to reference spectral data of a plurality of knownreference materials, and determining whether the target spectral datasubstantially matches a combination of at least two matching referencespectral data.
 40. A method for generating target material referencespectral data, the method comprising: obtaining target materialreference spectral data for a plurality of target materials usingillumination light from a tunable light source configured to emitillumination light having specific variable selected spectral output andspecific variable selected wavelength dependent intensity distribution;recording the target material reference spectral data for each of theplurality of target materials and recording the specific illuminationlight corresponding to each target material spectral data obtained. 41.The method of claim 40 wherein the illumination light for each targetmaterial is varied such that the wavelength intensities emanated fromthe target material are substantially the same across substantially allwavelengths measured.